The present invention relates to a mobile satellite communication terminal which is used for a mobile satellite communication system and is especially designed for satellite communication from indoors.
A conventional mobile satellite communication terminal is described in the following using FIG. 1 which shows a system diagram of the mobile satellite communication terminal.
The system of FIG. 1 includes a central earth station 1, plural mobile satellite communication terminals 40-1 to 40-3, and a satellite 2.
Terminals 40-1 to 40-3 are mobile satellite communication terminals having the structure, however they are placed in different positions. For example, terminal 40-1 is used outdoors, and is connected to central earth station 1 through satellite 2. Terminal 40-1 can communicate with the satellite 2 in a range of visibility even if the terminal is moved between mountains and buildings and the like.
Terminal 40-2 is located inside a building or the like. Communication by terminal 40-2 with satellite 2 can be performed at any a position from which satellite 2 can be seen, such as adjacent to window 21 provided in the building with a slight signal attenuation.
On the other hand, since terminal 40-3 is located at a position inside of the building and not near window 21, satellite 2 cannot be seen by terminal 40-3 and, transmitting and receiving signals to and from satellite 2 cannot be accomplished.
To communicate with satellite 2 using terminal 40-3, it must be moved to a place such as the window 21 or the like at which radio waves can be received.
As mentioned above, in the conventional mobile satellite communication system, communication cannot be performed when an obstacle is located between the mobile satellite communication terminal and the satellite.
Particularly, in a structure such as a building or the like, communication using the prior art terminals can be performed only from limited locations such as adjacent to a window and accordingly such terminals cannot be used with a high degree of freedom.
The above-mentioned mobile satellite communication system is described in documents "PTC 1993 proceedings, p. 835-p. 840" "INMARSAT-M PORTABLE MES".